Induction motor

ABSTRACT

Exemplary embodiments of the present invention relate to an induction motor including a stator having a circular cross-section and an inner passage having a longitudinal axis defining a bore, a solid core steel rotor having a circular cross-section rotatably disposed within the bore of the stator, and an air gap disposed between the rotor and the stator. A copper conductive layer is disposed on the steel rotor to increase the electrical conductance of the rotor. Exemplary embodiments adhere the copper conductive layer to the steel rotor using Hot Isostatic Pressing (HIP). The HIP process encloses the steel rotor and the copper conductive layer in a containment vessel, and adheres the conductive layer to the rotor by applying high temperature and high gas pressure to the outside of the containment vessel.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/987,839, filed on Jan. 10, 2011, which claims the benefit of priorityto U.S. Provisional Application Ser. No. 61/293,990 filed Jan. 11, 2010and to U.S. Provisional Application Ser. No. 61/323,073 filed Apr. 12,2010. The entire contents of the aforementioned applications areexpressly incorporated herein by reference in their entirety.

BACKGROUND

Induction motors known as solid rotor machines include a stator and asolid steel rotor rotatably disposed within a bore of the stator. Aconductive layer may be provided on the outer operating surface of therotor to increase the electrical conductance in the rotor. Conventionaltechniques of providing a copper layer on a steel rotor make use of airand electric means of propelling high-velocity molten copper against therotor surface. Examples of such conventional techniques include blastcoating and vapor deposition.

Conventional techniques do not produce adequate adhesion of the copperconductive layer to a solid core steel rotor. The copper-steel bondcreated by conventional techniques is not adequately strong to withstandhigh rotational speeds. Additionally, these techniques lead to oxidationand porosity of the copper conductive layer. Oxidation and porosity ofthe resulting copper conductive layer raises the electrical resistance,which necessitates a thicker conductive layer. The rise in electricalresistance increases the apparent air gap between the rotor and thestator, and leads to higher electrical losses in the motor.

SUMMARY

Exemplary embodiments of the present invention avoid the shortcomings ofconventional techniques of providing a conductive layer on a steel rotorby using Hot Isostatic Pressing (HIP) to adhere the conductive layer tothe steel rotor. In exemplary embodiments, the conductive layer is pureor substantially pure copper layer, and the rotor is a solid core steelrotor. The HIP process encloses the solid core steel rotor, a copperlayer sleeve, and two copper layer end caps in a containment vessel, andadheres the copper layer sleeve and end caps to the solid core steelrotor by applying high temperature and high gas pressure to the outsideof the containment vessel.

The HIP process creates a strong integral bond between the steel rotorand the copper layer. The resulting copper layer adhered to the rotor isnon-porous, which improves its performance as an electrical conductorbetween the rotor and the stator. The resulting copper layer is alsofree of contaminants like oxidation, moisture, oil, etc., and is notaffected by oxidation on the faying surfaces. These properties alsoenhance the electrical conductance between the rotor and the stator.

In accordance with one exemplary embodiment, an induction motor isprovided. The induction motor includes a stator having a circularcross-section and an inner passage having a longitudinal axis defining abore. The induction motor also includes a steel rotor having a circularcross-section rotatably disposed within the bore of the stator. Therotor includes an axial fan that directs incoming air in an axialdirection around the rotor.

In accordance with another exemplary embodiment, an induction motor isprovided. The induction motor includes a stator having a circularcross-section and an inner passage having a longitudinal axis defining abore. The induction motor also includes a solid core steel rotor havinga circular cross-section rotatably disposed within the bore of thestator. The induction motor further includes a layer of copperintegrally adhered to the outer surface of the solid core steel rotorusing Hot Isostatic Pressing (HIP).

In accordance with yet another exemplary embodiment, an induction motoris provided. The induction motor includes a stator having a circularcross-section and an inner passage having a longitudinal axis defining abore. The induction motor also includes a solid core steel rotor havinga circular cross-section rotatably disposed within the bore of thestator. The rotor includes an axial fan that directs incoming air in anaxial direction around the rotor. The induction motor further includes alayer of copper integrally adhered to the outer surface of the solidcore steel rotor using Hot Isostatic Pressing (HIP).

In accordance with still another exemplary embodiment, a method ofmanufacturing a solid core steel rotor in an induction motor isprovided. The method includes adhering a copper layer over an outersurface of the solid core steel rotor using Hot Isostatic Pressing(HIP).

In accordance with a further exemplary embodiment, an oil applicator forlubricating motor bearings is provided. The oil applicator includes feltapplicator that allows uniform distribution of oil from the oilapplicator. The oil applicator applies oil onto an oil slinger thatslings oil onto the motor bearings.

In accordance with yet another exemplary embodiment, a method oflubricating motor bearings is provided. The method includes distributingoil uniformly using a felt applicator of an oil applicator. The methodalso includes slinging the oil onto the motor bearings using an oilslinger in close proximity to the oil applicator.

In accordance with still another exemplary embodiment, an inductionmotor is provided. The induction motor includes bearings that arelubricated using an oil applicator. The oil applicator includes feltthat allows uniform distribution of oil from the oil applicator. The oilapplicator applies the oil onto an oil slinger that slings oil onto themotor bearings.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, aspects, features, and advantages ofexemplary embodiments will become more apparent and may be betterunderstood by referring to the following description taken inconjunction with the accompanying drawings, in which:

FIG. 1 illustrates an exemplary motor provided in accordance withexemplary embodiments.

FIG. 2 is a longitudinal section taken through an exemplary steel rotorthat is coated with an exemplary conductive layer using the HotIsostatic Pressing (HIP) process.

FIG. 3 is a transverse section taken through the middle of an exemplarysteel rotor that is coated with an exemplary conductive layer using theHIP process.

FIG. 4 is a flowchart that illustrates an exemplary method of adhering aconductive layer to a solid core steel rotor using the HIP process.

FIG. 5 illustrates an exemplary shaft body of a steel rotor before therotor is assembled with the conductive layer.

FIG. 6 illustrates an exemplary conductive layer end cap before theconductive layer end cap is assembled with the rotor.

FIG. 7 illustrates an exemplary conductive layer sleeve before theconductive layer sleeve is assembled with the rotor.

FIG. 8 illustrates the exemplary conductive layer sleeve of FIG. 7 andthe conductive layer end caps of FIG. 6 assembled over the exemplaryshaft body of FIG. 5.

FIG. 9 illustrates an exemplary containment chamber of HIP process thatis adhered to the conductive layer and rotor assembly of FIG. 8.

FIG. 10A illustrates a side view of an exemplary motor assemblyincluding a rotor and a fan shroud.

FIG. 10B illustrates a view of a motor fan assembly including a set offan blades provided integrally with a rotor and a set of stationaryvanes affixed to a fan shroud.

FIG. 11 illustrates an exemplary set of fan blades that are positionedaxially along an exemplary rotor.

FIG. 12 illustrates an exemplary set of fan blades that are positionedradially on an exemplary rotor, and a set of stationary vanes positionedon the stator to convert the radial flow into an axial flow.

FIG. 13A illustrates an exemplary shroud of a fan system havingexemplary stationary vanes affixed thereto.

FIG. 13B illustrates a stationary vanes before being affixed to theexemplary shroud of FIG. 13A.

FIG. 13C illustrates a close-up view of the exemplary stationary vanesaffixed to the exemplary shroud of FIG. 13A.

FIG. 14 illustrates an exemplary oil system for lubricating motorbearings.

FIG. 15 illustrates a longitudinal section through an exemplary oilapplicator in the exemplary oil system of FIG. 14.

DETAILED DESCRIPTION

Exemplary embodiments of the present invention relate to a solid rotorinduction motor including a stator having a circular cross-section andan inner passage having a longitudinal axis defining a bore, a solidcore steel rotor having a circular cross-section rotatably disposedwithin the bore of the stator, and an air gap disposed between the rotorand the stator. A copper conductive layer is disposed on the outersurface and end surfaces of the steel rotor to increase the electricalconductance of the rotor. Exemplary embodiments adhere the copperconductive layer to the steel rotor using Hot Isostatic Pressing (HIP).The HIP process encloses the steel rotor and the copper conductive layerin a containment vessel, and adheres the conductive layer to the rotorby applying high temperature and high gas pressure to the outside of thecontainment vessel.

The resulting conductive layer adhered to the rotor is non-porous, whichimproves its performance as an electrical conductor between the rotorand the stator. The resulting conductive layer is also free ofcontaminants like moisture, oil, etc., and is not affected by oxidationon the faying surfaces. These properties also enhance the electricalconductance between the rotor and the stator.

FIG. 1 illustrates an exemplary motor 10. The motor 10 includes bearings14, a stator 50, and a rotor 20 mounted within a bore of the stator 50.In exemplary embodiments, the motor 10 runs typically between about30,000 and 100,000 rpm.

The stator 50 includes stator winding 56, an inner surface 54 facing therotor 20, and a bore 52 extending along a longitudinal axis X.

An air gap 60 is formed between the inner surface 54 of the stator 50and a conductive layer 30 provided over the outer surface of the rotor20. In exemplary embodiments, the air gap 60 has a thickness of 0.1inches. Cool air is introduced through the rotor 20, and is thereafterapplied axially through the air gap 60.

The size of the air gap 60 has significance in the high-speed technicalapplications of the motor 10, especially with relation to itsefficiency. More specifically, increasing the air gap optimizes theefficiency of the motor by decreasing drag losses. As such, the air gapin exemplary embodiments has an average thickness of 0.1 inches, whichis substantially larger than conventional air gaps which have an averagethickness of 0.015 inches. U.S. Pat. No. 5,473,211 discusses therelationship between the air gap thickness and motor efficiency, and isherein incorporated in its entirety by reference.

Providing a thicker air gap in exemplary embodiments permits sufficientcooling air to be applied axially to the air gap 60, which provides aheat sink for both the rotor 20 and the stator 50. An unexpected resultof exemplary embodiments is that the flow of cooling air through the airgap 60 adequately cools the rotor 20 and the stator 50 with minimumpower consumption. The motor 10 may thus operate efficiently without anexternal or auxiliary mechanism cooling the rotor 20 and the stator 50.

The rotor 20 is rotatably disposed within the bore 52 of the stator 50along the longitudinal axis X. The rotor 20 rotates relative to thestator 50. The rotor 20 includes a shaft body 22, and a conductive layer30 that is adhered to the entire operating outer surface of the rotor 20using the Hot Isostatic Pressing (HIP) process. The shaft body 22 ismagnetically and electrically conductive, and may be solid or hollow.The outer surface of the shaft body is integral, but can be identifiedas having an outer circumferential portion 24 and two end portions 26and 28.

The conductive layer 30 is a material with a high electrical conductanceprovided to serve as a conductor for the electrical current flowingthrough and over the rotor 20. The electrical current traveling throughand over the rotor should substantially run in the conductive layer inorder to minimize current-heat losses.

In an exemplary embodiment, the rotor 20 in the motor 10 has aconductive layer 30 adhered to the outer surface of the shaft body 22 ofthe rotor 20 using Hot Isostatic Pressing (HIP). In the exemplaryembodiment, the rotor 20 is a solid core steel rotor, and the conductivelayer 30 is pure or substantially pure copper. The copper layer 30 mayhave an average thickness of about 1-3 mm, with a preferred embodimenthaving a thickness of about 1 mm. The ideal copper layer thickness for aparticular motor is determined based on variables specific to the motor,e.g., flux path, flux losses, etc.

FIGS. 2 and 3 illustrate an exemplary shaft body 22 of a rotor 20 coatedwith an exemplary copper layer 30 using the HIP process. The finalcopper layer 30—adhered to the shaft body 22—is a single, integral unit,but may be identified as having three portions in an exemplaryembodiment: a copper layer sleeve 32 and two copper layer end caps 34and 36. The copper layer sleeve 32 is disposed on the outercircumferential portion 24 of the shaft body 22 that runs along thestator 50. The copper layer sleeve 32 serves as a conductor for the fluxflowing across the air gap 60 to induce a current flow in the conductivelayer. The copper layer end caps 34 and 36 are disposed on the endportions 26 and 28, respectively, of the shaft body 22. The copper layerend caps 34 and 26 provide a short circuit flux path across the rotor 20to engage with complementary stator poles, which is necessary for theinduction machine to function. In other exemplary embodiments, thecopper layer 30 may be identified as having fewer or more than theabove-identified portions.

In an exemplary embodiment, the copper layer 30 has uniform thicknessover the shaft body 22, such that the copper layer sleeve 32 and theconductive layer end caps 34 and 36 have the same thickness. In anotherexemplary embodiment, the copper layer 30 is thicker at the conductivelayer end caps 34 and 36 than at the copper layer sleeve 32.

FIG. 2 is a longitudinal section taken through a rotor 20 with a copperlayer 30 adhered to the outer surface of the rotor 20. The rotor 20includes an outer circumferential portion 24 and two end portions 26 and28. The copper layer sleeve 32 extends over the outer circumferentialportion 24 of the shaft body 22 to join electrically with copper layerend caps 34 and 36. In addition, the two copper layer end caps 34 and 36are electrically attached to the end portions 26 and 28, respectively,of the shaft body 22.

FIG. 3 is a transverse section taken through the middle of a rotor 20with a copper layer 30 adhered to the outer surface of the rotor 20. Theshaft body 22 is a steel body. The outer circumferential portion 24 ofthe shaft body 22 is coated with the copper layer sleeve 32.

Exemplary embodiments of the present invention avoid the shortcomings ofconventional techniques of providing a copper conductive layer on asteel rotor by using the Hot Isostatic Pressing (HIP) process to adherethe copper layer 30 to the shaft body 22 of the rotor 20. The HIPprocess subjects the outside of a high-pressure containment vesselenclosing the shaft body 22 and the copper layer 30 to both elevatedtemperature and isostatic gas pressure. The elevated temperature andisostatic gas pressure causes the copper layer 30 to integrally adhereto the shaft body 22.

FIG. 4 is a flowchart that illustrates an exemplary method of adheringthe copper layer 30 to the steel shaft body 22 of the rotor 20 using theHIP process. In step 1 of FIG. 4, the copper layer 30 and the rotor 20are pre-processed before the start of the HIP process. Pre-processingmay involve cleaning the copper layer and the rotor to removecontaminants like oil, oxidation, moisture, etc. Pre-processing may alsoinvolve ensuring that the copper layer and the rotor are free ofcontaminants. Pre-processing may further involve sealing the copperlayer and the rotor, e.g., in vacuum packs, to ensure that the copperlayer and rotor do not become re-contaminated before their transfer tothe HIP location.

FIG. 5 illustrates the shaft body 22 of the rotor 20 before or afterpre-processing step 1, i.e., before the rotor is assembled with thecopper layer. FIG. 6 illustrates the copper layer end cap 34, 36 beforeor after pre-processing step 1, i.e., before the copper layer end capsare assembled with the rotor. FIG. 7 illustrates the copper layer sleeve32 before or after pre-processing step 1, i.e., before the copper layersleeve is assembled with the rotor.

In steps 2 and 3 of FIG. 4, the copper layer 30 and the rotor 20 areassembled together before the HIP process adheres the copper layer tothe rotor. The copper layer sleeve 32 is assembled over the outercircumferential portion 24 of the shaft body 22 of the rotor 20. Thecopper layer end caps 34 and 36 are assembled over the end portions 26and 28, respectively, of the shaft body 22 of the rotor 20. In theassembly, the copper layer end caps 34 and 36 abut the copper layersleeve 32. This negates the need for a stressed weld between the sleeveand the end caps.

FIG. 8 illustrates the copper layer sleeve 32 assembled over the outercircumferential portion 24 of the shaft body 22 of the rotor 20, and thecopper layer end caps 34 and 36 assembled over the end portions 26 and28, respectively, of the shaft body 22 of the rotor 20. In thisassembly, the copper layer 30 fits loosely over the rotor 20. However,the copper layer and the rotor are clean and free of contaminants, andthere is no oxidation on the faying surfaces.

Steps 4-7 of FIG. 4 outline the HIP process. In step 4, the rotorassembly is introduced into the containment chamber 70 of the HIPprocess. In step 5, the containment chamber is welded to the shaft body22 assembled with the copper layer 30. A high vacuum is pulled on thecontainment chamber and the chamber is subjected to high temperatures toremove air and moisture through a gas introduction spigot 72. In anexemplary embodiment, the containment chamber may be purged with aninert gas, such as argon, prior to being evacuated. In step 6, the gasintroduction spigot 72 is sealed off and the entire assembly issubjected to high temperature and high pressure.

FIG. 9 illustrates an exemplary containment chamber 70 adhered to therotor assembly, and an exemplary gas introduction spigot 72 attached tothe containment chamber 70.

In step 7, the high temperature and high pressure outside thecontainment chamber causes the copper layer 30 to integrally adhere tothe shaft body 22 of the rotor 20. More specifically, the copper layersleeve 32 adheres integrally to the outer circumferential portion 24 ofthe shaft body 22, and the copper layer end caps 34 and 36 adheresintegrally to the end portions 26 and 28, respectively, of the shaftbody 22. The HIP process also adheres the copper layer sleeve 32 to thecopper layer end caps 34 and 36 such that the entire copper layer 30 andthe rotor 20 is a single integral unit.

The high temperature and high gas pressure employed in the HIP processeliminate internal voids in the copper layer 30, and create a clean anduniform bond between the copper layer 30 and the rotor 20. The resultingcopper layer is not porous, which improves its performance as anelectrical conductor between the rotor and the stator. The resultingcopper layer is also free of contaminants like oxidation, moisture, oil,etc., and is not affected by oxidation on the faying surfaces. Theseproperties also enhance the electrical conductance between the rotor andthe stator. Conventional techniques of providing a copper layer on asteel rotor cannot provide these advantageous characteristics.

In step 8 of FIG. 4, after the completion of the HIP process, thecontainment chamber 70 is machined off from the rotor assembly. FIG. 2illustrates the rotor assembly after the containment chamber has beenmachined off.

In another exemplary embodiment, the rotor 20 in the motor 10 has aconductive layer 30 adhered to the outer surface of the shaft body 22 ofthe rotor 20 using Hot Isostatic Pressing (HIP). The rotor 20 is a solidcore steel rotor, and the conductive layer 30 is pure or substantiallypure copper. In this exemplary embodiment, an exemplary fan system ofthe motor 10 includes a set of fan blades 40 affixed to the outersurface of the rotor 20. An exemplary fan system also includes a set ofstationary vanes 42 affixed to a fan shroud 44. The fan blades 40 andthe stationary vanes 42 are configured to allow incoming air to flowthrough the air gap 60 substantially in an axial direction. This allowsthe fan blades 40 to impart a velocity increase to the incoming coolingair, and to increase the static pressure of the incoming air. Thisinduces the incoming air to flow into an opening of the air gap 60 at ahigh velocity.

FIG. 10A illustrates a side view of an exemplary motor assemblyincluding a rotor 20 and a fan shroud 44. FIG. 10B illustrates a view ofa motor fan assembly including a set of fan blades 40 providedintegrally with a rotor and a set of stationary vanes 42 affixed to afan shroud.

In an exemplary configuration, illustrated in FIG. 11, the fan blades 40are positioned axially around the rotor 20, and a set of stationaryvanes 42 is used to divert the radial flow into an axial flow along theair gap 60. The incoming air arriving from the axial fan blades 40 has atangential component and an axial component. The stationary vanes 42turn the net velocity vector of the incoming air axially. This axialturning of the net velocity vector significantly increases the staticpressure, thus inducing the incoming air to flow into an opening of theair gap 60 at high speed and high pressure.

In another exemplary embodiment, the rotor 20 in the motor 10 has anaxial fan 40 affixed to the outer surface of the rotor 20 to introduceair axially into the air gap 60. The fan blades 40 are configured toallow incoming air to flow through the air gap 60 substantially in anaxial direction. This allows the fan blades 40 to impart a velocityincrease to the incoming cooling air, and to increase the staticpressure of the incoming air. This induces the incoming air to flow intoan opening of the air gap 60 at a high velocity.

In yet another exemplary configuration, illustrated in FIG. 12, the fanblades 40 are positioned radially on the rotor 20, and a divertingmechanism 46 positioned downstream from the fan blades 40 directsincoming air from a radial direction to an axial direction along the airgap 6. A set of stationary vanes 42 is used to further direct theincoming air into an axial flow along the air gap 60. The set ofstationary vanes 42 is provided integrally on the inner surface 54 ofthe stator 50. The set of stationary vanes 42 is disposed downstreamfrom the fan blades 40 and the diverting mechanism 46.

The fan system of the motor includes an exemplary shroud 44 which guidesthe incoming air into contact with the fan blades 40 and the stationaryvanes 42. In exemplary embodiments, the shroud 44 may have an inletcurvature to assist in introducing the incoming air into the rotatingblading. In an exemplary embodiment, the shroud 44 may be fixed to thestator winding 56 of the stator 50. FIG. 13A illustrates a longitudinalsection taken through an exemplary rotor 20 with an exemplary shroud 44having exemplary stationary vanes 42 affixed thereto. FIG. 13Billustrates a detailed view of the exemplary vanes 42 before beingaffixed to the exemplary shroud 44 of FIG. 13A. FIG. 13C illustrates aclose-up view of the exemplary stationary vanes 42 affixed to theexemplary shroud 44 of FIG. 13A.

The set of fan blades 40 is affixed to the rotor 20 after the HIPprocess, i.e., after step 8 of FIG. 4.

In still another exemplary embodiment, an oil system is provided forlubricating the bearings of a motor. The oil system provided byexemplary embodiments is designed and configured to provide lubricationto high-speed motor bearings, while limiting oil flow to prevent heatbuild-up that can be caused by excessive oil flow.

A motor provided by exemplary embodiments, operating at about 42,000rpm, requires an oil flow of about 0.0025 liters per minute to lubricateand cool the bearings of the motor. The speed of oil injected into thehigh-speed bearing needs to be close to the peripheral speed of thebearing, i.e., about 220 feet per second. One conventional methodologyof achieving this oil speed uses an oil nozzle to supply the oil to thebearing and raises an upstream oil pressure to about 260 psig. Thismethodology requires a corresponding nozzle opening of about 0.0015inches in diameter. Such a small nozzle opening is not suitable for thepurposes of lubricating and cooling a motor bearing, as it carries ahigh risk of blockage and may negatively affect good oil filtering andpassage cleanliness in the oil lubrication system.

Another conventional methodology introduces the oil flow to the motorbearing from an oil reservoir via a felt wick. The felt wicks or liftsoil from an oil reservoir. The felt wick is located close to a conicalsurface on the shaft of the motor that acts as an oil slinger. Thismethodology may be practical for use with small turbochargers, but theability of a wick to lift oil from a nearby oil reservoir is limited bythe height of the raised portion of the wick from the oil reservoir.

The oil system taught by exemplary embodiments overcome the limitationsof conventional methodologies by using a small oil pump to introduce oilto a wick which then transfers the oil to a motor bearing to lubricateand cool the bearing. FIG. 14 illustrates an exemplary oil system 80 forlubricating motor bearings 14. The oil system 80 includes an oil sump 82which is a oil reservoir provided at the bottom of the motor. Oil usedto lubricate the motor bearings pools in the oil sump 82. Oil from theoil sump 82 is filtered in an oil filter 84 to remove undesirableparticles from the oil before it is used to lubricate the bearings.

After filtration, the oil is then pumped by a pump 86, e.g., anelectric-powered piston pump, through an oil-to-ambient heat exchanger88 which cools the oil to be supplied to the motor bearings 14. Hightemperatures may reduce the viscosity of oil, which makes the oil filmtoo thin for effective lubrication of the bearings. To maintain theviscosity of the oil, the heat exchanger 88 removes excess heat from theoil before it is used in lubricating the motor bearings 14. In anexemplary embodiment, the entire flow of oil pumped by the pump 86 ispassed through the heat exchanger 88. A small portion of the pumped flowis directed to the bearings 14, and the balance of the pumped flow isdirected to the oil sump 82. The pumped oil flow size (i.e., the flowsize of the oil pumped at the pump 86) can be much greater than the oilflow that eventually reaches and that is required by the motor bearings14. A suitable pump can thus be secured from commonly available pumpsuppliers.

The filtered and cooled oil is then distributed between two sets oforifices based on the lubrication needs in the motor: one or more mainflow control orifices 90 and one or more secondary flow control orifices92. The main flow control orifices 90 return unused oil to the oil sump82. The second flow control orifices 92 provide the oil to one or moreoil applicators 94 that are in close proximity or contact with an oilslinger 96 (FIG. 15), which, in turn delivers the oil to the motorbearings 14. The oil flows into the oil applicators 94 and is thereupontransferred to the oil slinger 96. In exemplary embodiments, the oilapplicators 94 may include a shortened wick through which the oil istransferred to the oil slinger 96. In exemplary embodiments, the oilapplicators 94 may include felt which is highly oil absorbent and hasgreat wicking capabilities.

FIG. 15 illustrates a longitudinal section through an exemplary oilapplicator 94 in the exemplary oil system 80 of FIG. 14. The oilapplicator 94 applies oil to the oil slinger 96 which slings the oilarriving through the secondary oil flow control orifices 92. Theslinging action transfers the oil to the lip of the oil slinger 96,after which is it deposited onto the bearings 14. The oil applicator 94is also equipped with one or more pieces of felt 98 which allows uniformdistribution of the oil slung by the oil slinger 96, and ensures that anoptimum amount of oil is used to lubricate the bearings 14.

In a further exemplary embodiment, a motor 10 is provided with bearings14 lubricated using the exemplary oil system 80 illustrated in FIGS. 14and 15.

One of ordinary skill in the art will appreciate that the presentinvention is not limited to the specific exemplary embodiments describedherein. Many alterations and modifications may be made by those havingordinary skill in the art without departing from the spirit and scope ofthe invention. Therefore, it must be expressly understood that theillustrated embodiments have been shown only for the purposes of exampleand should not be taken as limiting the invention, which is defined bythe following claims. One of ordinary skill in the art will appreciatethat any number of the illustrated embodiments may be implementedtogether. These claims are to be read as including what they set forthliterally and also those equivalent elements which are insubstantiallydifferent, even though not identical in other respects to what is shownand described in the above illustrations.

1. An induction motor, comprising: a stator including an inner passagehaving a longitudinal axis defining a bore; a steel rotor rotatablydisposed within the bore of the stator, the steel rotor comprising: acylindrical portion extending between a proximal end and a distal end, aproximal end portion disposed at the proximal end and extendingorthogonally to the cylindrical portion, and a distal end portiondisposed at the distal end and extending orthogonally to the cylindricalportion; and a Hot Isostatic Pressing (HIP) layer of copper integrallyadhered to an outer surface of the steel rotor, the HIP layer of coppercomprising: a cylindrical HIP layer of copper integrally adhered to thecylindrical portion of the rotor, a proximal HIP layer of copperintegrally adhered to the proximal end portion of the rotor, and adistal HIP layer of copper integrally adhered to the distal end portionof the rotor; wherein the proximal HIP layer of copper and the distalHIP layer of copper are configured to provide a short circuit flux pathacross the rotor to engage with complementary poles of the stator. 2.The induction motor of claim 1, wherein the cylindrical HIP layer ofcopper, the proximal HIP layer of copper and the distal HIP layer ofcopper form an integral unit.
 3. The induction motor of claim 1, whereinthe cylindrical HIP layer of copper, the proximal HIP layer of copperand the distal HIP layer of copper have the same thickness.
 4. Theinduction motor of claim 1, wherein the cylindrical HIP layer of copperhas a smaller thickness than the proximal HIP layer of copper and thedistal HIP layer of copper.
 5. The induction motor of claim 1, whereinthe HIP layer of copper fits loosely over the steel rotor.
 6. Theinduction motor of claim 1, further comprising: an air gap disposedbetween an outer surface of the rotor and an inner surface of thestator; a fan shroud; and a fan system, comprising: a set of fan bladesaffixed to an outer surface of the rotor, and a set of vanes affixed tothe fan shroud; wherein the fan blades affixed to the rotor and thevanes affixed to the fan shroud are pneumatically coupled to each otherand cooperatively configured to direct cooling air to flow through theair gap axially around the rotor.
 7. The induction motor of claim 1,further comprising: one or more motor bearings; and an oil lubricationsystem for lubricating the one or more motor bearings, the oillubrication system comprising: an oil reservoir for storing alubricating oil used to lubricate the one or more motor bearings, an oilpump coupled to the oil reservoir for pumping the oil from the oilreservoir to a vertical level of the one or more motor bearings, a firstoutlet mechanism coupled to the oil pump for returning a first portionof the pumped flow of the oil to the oil reservoir, and a second outletmechanism coupled to the oil pump for transferring a second portion ofthe pumped flow of the oil to an oil applicator for transferring the oilonto the motor bearings.
 8. The induction motor of claim 7, wherein theoil lubrication system further comprises: an oil filter having an inletcoupled to the oil reservoir and an outlet coupled to the oil pump forfiltering the oil before the oil is pumped by the oil pump; and anoil-to-ambient heat exchanger for cooling the filtered oil.
 9. Theinduction motor of claim 8, wherein the entire flow of oil pumped by theoil pump is passed through the heat exchanger.
 10. The induction motorof claim 7, wherein the first portion of the flow of the oil to the oilreservoir is larger than the second portion of the flow of the oil tothe oil applicator.
 11. The induction motor of claim 7, wherein the oilapplicator comprises: an oil slinger configured to receive the oil fromthe second outlet mechanism and to transfer the oil by a slinging actionto a lip of the oil slinger, the oil slinger comprising the lipconfigured to receive the oil due to the slinging action and to transferthe oil to the motor bearings; and a piece of felt configured touniformly distribute the oil slung by the oil slinger.
 12. The inductionmotor of claim 7, wherein the oil lubrication system is configured totransfer the oil to the motor bearings at a peripheral speed of themotor bearings.
 13. The induction motor of claim 12, wherein the oil istransferred to the motor bearings at an average speed of 220 feet persecond.
 14. An induction motor, comprising: a stator including an innerpassage having a longitudinal axis defining a bore; a steel rotorrotatably disposed within the bore of the stator; an air gap disposedbetween an outer surface of the rotor and an inner surface of thestator; a fan shroud; and a fan system, comprising: a set of fan bladesaffixed to an outer surface of the rotor, and a set of vanes affixed tothe fan shroud; wherein the fan blades affixed to the rotor and thevanes affixed to the fan shroud are pneumatically coupled to each otherand cooperatively configured to direct cooling air to flow through theair gap axially around the rotor.
 15. The induction motor of claim 14,wherein the fan blades and the vanes are cooperatively configured toincrease the static pressure of the air in the air gap.
 16. Theinduction motor of claim 14, wherein the fan blades and the vanes arecooperatively configured to increase the speed of the air flowing intothe air gap.
 17. The induction motor of claim 14, wherein the fan shroudhas an inlet curvature configured to assist in introducing the air intothe air gap.
 18. The induction motor of claim 14, wherein the motorlacks an external cooling mechanism for cooling the stator and therotor.
 19. An induction motor, comprising: a stator including an innerpassage having a longitudinal axis defining a bore; a steel rotorrotatably disposed within the bore of the stator; a Hot IsostaticPressing (HIP) layer of copper integrally adhered to an outer surface ofthe rotor; an air gap disposed between an outer surface of the HIP layerof copper and an inner surface of the stator; a fan shroud; and a fansystem, comprising: a set of fan blades affixed to an outer surface ofthe rotor, and a set of vanes affixed to the fan shroud; wherein the fanblades affixed to the rotor and the vanes affixed to the fan shroud arepneumatically coupled to each other and cooperatively configured todirect cooling air to flow through the air gap axially around the rotor.20. A method of assembling a rotor for an induction motor, the methodcomprising: providing a steel rotor comprising: a cylindrical portionextending between a proximal end and a distal end, a proximal endportion disposed at the proximal end and extending orthogonally to thecylindrical portion, and a distal end portion disposed at the distal endand extending orthogonally to the cylindrical portion; and integrallyadhering a cylindrical Hot Isostatic Pressing (HIP) layer of copper tothe cylindrical portion of the rotor; integrally adhering a proximal HIPlayer of copper to the proximal end portion of the rotor; and integrallyadhering a distal HIP layer of copper to the distal end portion of therotor; wherein the proximal HIP layer of copper and the distal HIP layerof copper are configured to provide a short circuit flux path across therotor to engage with complementary poles of a stator.